Direct measurements of inverse magnetocaloric effects in metamagnetic shape-memory alloy NiCoMnIn

TLDR

The study aims to disentangle electronic, lattice, and magnetic contributions to the inverse magnetocaloric effect in Ni₄₅Co₅Mn₅₀₋ₓInₓ by performing magnetization, magnetocaloric, and specific‑heat measurements across a wide field and temperature range. Measurements included magnetization, magnetocaloric effect, and specific‑heat studies in steady and pulsed magnetic fields up to 15 T, with direct adiabatic temperature change observations and entropy‑sector analyses of charge, spin, and lattice contributions. A maximum adiabatic temperature drop of 12.8 K was recorded, and analysis shows the lattice sector dominates the inverse magnetocaloric response.

Abstract

To clarify the electronic, lattice, and magnetic contribution to the inverse magnetocaloric effect (IMCE) in the metamagnetic shape-memory alloy ${\mathrm{Ni}}_{45}{\mathrm{Co}}_{5}{\mathrm{Mn}}_{50\ensuremath{-}x}{\mathrm{In}}_{x}$, magnetization, magnetocaloric effect, and specific-heat measurements were carried out in a wide range of fields and temperatures. The IMCEs of ${\mathrm{Ni}}_{45}{\mathrm{Co}}_{5}{\mathrm{Mn}}_{36.7}{\mathrm{In}}_{13.3}$ were directly measured as adiabatic temperature changes in pulsed fields of up to 15 T. A maximum temperature decrease of $\ensuremath{-}12.8$ K was observed. The low-temperature specific heats in both the austenitic and the martensitic phases of ${\mathrm{Ni}}_{45}{\mathrm{Co}}_{5}{\mathrm{Mn}}_{36.5}{\mathrm{In}}_{13.5}$ were measured by using steady fields. Through analyses of the data, the entropy changes in charge (1.2 J/kg K), spin $(\ensuremath{-}29$ J/kg K), and lattice (51 J/kg K) sectors were individually evaluated. The result demonstrates the dominant role of the lattice sector in inverse MCEs in this material.